Low pH Sites Research Articles

Surface application of cement kiln dust and lime to forage land: Effect on forage yield, tissue concentration and accumulation of nutrients

Cement kiln dust (CKD), a by-product of the cement industry currently being landfilled, may be a beneficial soil amendment. A 2-yr field forage trial compared the effect of surface applications of CKD and lime on forage yield and the concentration and accumulation of N, P, K, Ca, Mg, Mn, Cu, Zn and B in the forage tissue. Seven soil treatments in three blocks were established on three low pH sites: (1) a check plot with neither lime or CKD added; (2) lime application based on the recommendation from soil analysis; (3) lime at 1.5 times the recommended application; (4) CKD applied at the recommended application; (5) CKD at 1.5 times the recommended application; (6) CKD applied on a neutralizing equivalent basis at the recommended application rate; and (7) CKD on a neutralizing equivalent basis at 1.5 times the recommended lime application; equivalence based on CKD’s apparent neutralizing value at 75% that of lime. In 1998, as tissue concentrations of K, Ca, Cu, and Mn increased with CKD application, the concentrations of N, P and Mg decreased, and in 1999, as the concentrations of Ca, K increased, the concentrations of N, P, Mg Mn, Zn decreased. Lime application increased the concentration of Mg (1998) and Ca and Mg (1999). The concentration of the other nutrients either decreased or were not significantly affected. In1998, forage yield and accumulation of Ca, K, Mn, Cu, Zn and B all increased with CKD addition, whereas the accumulation of Mg increased with lime addition. In 1999, forage yield and accumulation of N, P, K, Ca, Cu, Zn and B in the forage tissue all increased with CKD addition. These results were identified by principal component analysis (PCA). Surface applied CKD increased forage yield to a greater extent than lime. It was also a more readily available source of Ca and K than lime.Key words: Cement kiln dust

Caveolin-1-Dependent Infectious Entry of Human Papillomavirus Type 31 in Human Keratinocytes Proceeds to the Endosomal Pathway for pH-Dependent Uncoating

High-risk human papillomaviruses (HPVs) are small nonenveloped DNA viruses with a strict tropism for squamous epithelium. The viruses are causative agents of cervical cancer and some head and neck cancers, but their differentiation-dependent life cycles have made them difficult to study in simple cell culture. Thus, many aspects of early HPV infection remain mysterious. We recently showed the high-risk HPV type 31 (HPV31) enters its natural host cell type via caveola-dependent endocytosis, a distinct mechanism from that of the closely related HPV16 (Smith et al., J. Virol. 81:9922-9931, 2007). Here, we determined the downstream trafficking events after caveolar entry of HPV31 into human keratinocytes. After initial plasma membrane binding, HPV31 associates with caveolin-1 and transiently localizes to the caveosome before trafficking to the early endosome and proceeding through the endosomal pathway. Caveosome-to-endosome transport was found to be Rab5 GTPase dependent. Although HPV31 capsids were observed in the lysosome, Rab7 GTPase was dispensable for HPV31 infection, suggesting that viral genomes escape from the endosomal pathway prior to Rab7-mediated capsid transport. Consistent with this, the acidic pH encountered by HPV31 within the early endosomal pathway induces a conformational change in the capsid resulting in increased DNase susceptibility of the viral genome, which likely aids in uncoating and/or endosomal escape. The entry and trafficking route of HPV31 into human keratinocytes represents a unique viral pathway by which the virions use caveolar entry to eventually access a low-pH site that appears to facilitate endosomal escape of genomes.

Modelling phosphate adsorption to the soil: Application of the non-ideal competitive adsorption model

Phosphorus (P) transport in subsurface runoff has increased despite the limited mobility of P in soils. This study investigated the ability of the non-ideal competitive adsorption (NICA) model to describe phosphate (PO 4) adsorption for soils in southern Quebec (Canada). We measured the surface charge and PO 4 adsorption capacity for 11 agricultural soils. Using the experimental data and a nonlinear fitting function, we derived the NICA model parameters. We found that the NICA model described accurately the surface charge of these soils with a mean R 2 > 0.99, and described the adsorption data with a mean R 2 = 0.96. We also found that the variable surface charge was distributed over the two binding sites with the low pH sites demonstrating a stronger binding energy for hydroxyl and PO 4 ions. We established that the NICA model is able to describe P adsorption for the soils considered in this study.

Changes to the structure ofSphingomonasspp. communities associated with biodegradation of the herbicide isoproturon in soil

The phenyl-urea herbicide isoproturon is a major contaminant of surface and ground-water in agricultural catchments. Earlier work suggested that within-field spatial variation of isoproturon degradation rate resulted from interactions between catabolizing Sphingomonas spp. and pH. In the current study, changes to the structure of Sphingomonas communities during isoproturon catabolism were investigated using Sphingomonas-specific 16S rRNA gene primers. Growth-linked catabolism at high-pH (>7.5) sites was associated with the appearance of multiple new denaturing gradient gel electrophoresis (DGGE) bands. At low-pH sites, there was no change in DGGE banding at sites in which there was cometabolism, but at sites in which there was growth-linked catabolism, degradation was associated with the appearance of a new band not present at high pH sites. Sequencing of DGGE bands indicated that a strain related to Sphingomonas mali proliferated at low pH sites, while strain Sphingomonas sp. SRS2, a catabolic strain identified in earlier work, together with several further Sphingomonas spp., proliferated at high-pH sites. The data indicate that degradation was associated with complex changes to the structure of Sphingomonas spp. communities, the precise nature of which was spatially variable.

Occurrence of non‐mycorrhizal plant species in south Swedish rocky habitats is related to exchangeable soil phosphate

Summary Plant species that do not typically form mycorrhiza are most likely to be successful under conditions where mycorrhizal fungi are not important for plant coexistence or where the costs of symbiosis outweigh the benefits. The relative occurrence of non‐mycorrhizal species was investigated in relationship to exchangeable soil P in herbaceous vegetation, where arbuscular mycorrhizal (AM) associations are generally common. We investigated a total of 439 sites in rocky habitats with sparse vegetation and 110 meadows with dense vegetation. In both rocky habitats and meadows, soil pH was inversely related to exchangeable P. In rocky habitats plant species richness increased greatly between pH 3 and 5 and was also inversely related to P. Plant communities in rocky habitats contained a relatively larger proportion of non‐mycorrhizal species than those in meadows. More non‐mycorrhizal species occurred at high soil P in the rocky habitats, but no such relation was found in meadows. Non‐mycorrhizal species in rocky habitats were most common at low soil pH (high P availability). Plant species that thrived at extreme soil pH were often non‐mycorrhizal. The occurrence of fewer non‐mycorrhizal plants in meadows than in rocky habitats supports the hypothesis that AM associations are more important in ecosystems with intense competition among plants. In rocky habitats, where abiotic stress may restrict photosynthesis more than nutrient limitation does, it is adaptive for plant species to utilize strategies other than mycorrhiza, particularly at low pH sites where P availability is likely to be adequate.

PH-induced Conversion of the Transport Lectin ERGIC-53 Triggers Glycoprotein Release

The recycling mannose lectin ERGIC-53 operates as a transport receptor by mediating efficient endoplasmic reticulum (ER) export of some secretory glycoproteins. Binding of cargo to ERGIC-53 in the ER requires Ca2+. Cargo release occurs in the ERGIC, but the molecular mechanism is unknown. Here we report efficient binding of purified ERGIC-53 to immobilized mannose at pH 7.4, the pH of the ER, but not at slightly lower pH. pH sensitivity of the lectin was more prominent when Ca2+ concentrations were low. A conserved histidine in the center of the carbohydrate recognition domain was required for lectin activity suggesting it may serve as a molecular pH/Ca2+ sensor. Acidification of cells inhibited the association of ERGIC-53 with the known cargo cathepsin Z-related protein and dissociation of this glycoprotein in the ERGIC was impaired by organelle neutralization that did not impair the transport of a control protein. The results elucidate the molecular mechanism underlying reversible lectin/cargo interaction and establish the ERGIC as the earliest low pH site of the secretory pathway.

Metal Ions Binding to Natural Organic Matter Extracted from Wheat Bran: Application of the Surface Complexation Model

Ions binding to solid organic matter was investigated in this study. A simple surface complexation model, the diffuse double-layer model, was used to describe Pb(II), Cd(II), Zn(II), and Ni(II) binding to a lignocellulosic substrate extracted from wheat bran. The lignocellulosic substrate was represented by two acid sites: a low-pH (“carboxylic”) site and a high-pH (“phenolic”) site, the phenolic-type sites contributing significantly to the binding behavior, even at relatively low pH. By using the previously determined concentrations of sites and acidity constants, the surface complexation model was applied to Pb, Cd, Zn, and Ni binding as a function of pH in a 0.1 M NaNO3 medium. The model fits were good over a wide range of pH (2<pH<10). The parameters deduced from these single-metal data were then used to predict metals binding under different conditions. The model accounted well for the change in solid concentration ([solid]=0.2–1 g/L), metal concentration ([M]=2×10−5 to 1.4×10−3 M), and ionic strength ([NaNO3]=0.01–0.1 M). It also allowed reasonably good prediction of the competition between up to five metals for the available sites.

Seasonal variations in microbial populations and environmental conditions in an extreme acid mine drainage environment.

Microbial populations, their distributions, and their aquatic environments were studied over a year (1997) at an acid mine drainage (AMD) site at Iron Mountain, Calif. Populations were quantified by fluorescence in situ hybridizations with group-specific probes. Probes were used for the domains Eucarya, Bacteria, and Archaea and the two species most widely studied and implicated for their role in AMD production, Thiobacillus ferrooxidans and Leptospirillum ferrooxidans. Results show that microbial populations, in relative proportions and absolute numbers, vary spatially and seasonally and correlate with geochemical and physical conditions (pH, temperature, conductivity, and rainfall). Bacterial populations were in the highest proportion (>95%) in January. Conversely, archaeal populations were in the highest proportion in July and September ( approximately 50%) and were virtually absent in the winter. Bacterial and archaeal populations correlated with conductivity and rainfall. High concentrations of dissolved solids, as reflected by high conductivity values (up to 125 mS/cm), occurred in the summer and correlated with high archaeal populations and proportionally lower bacterial populations. Eukaryotes were not detected in January, when total microbial cell numbers were lowest (<10(5) cells/ml), but eukaryotes increased at low-pH sites ( approximately 0.5) during the remainder of the year. This correlated with decreasing water temperatures (50 to 30 degrees C; January to November) and increasing numbers of prokaryotes (10(8) to 10(9) cells/ml). T. ferrooxidans was in highest abundance (>30%) at moderate pHs and temperatures ( approximately 2.5 and 20 degrees C) in sites that were peripheral to primary acid-generating sites and lowest (0 to 5%) at low-pH sites (pH approximately 0.5) that were in contact with the ore body. L. ferrooxidans was more widely distributed with respect to geochemical conditions (pH = 0 to 3; 20 to 50 degrees C) but was more abundant at higher temperatures and lower pHs ( approximately 40 degrees C; pH approximately 0.5) than T. ferrooxidans.

The effects of stream acidity on benthic invertebrate communities in the south‐eastern United States

SUMMARY1. Patterns in invertebrate community structure were determined from analysis of benthic samples taken quarterly for 1 year from four sites in the Great Smoky Mountains National Park (GSMNP). Sites ranged in baseflow pH from 4.5 to 6.8, with a corresponding range in inorganic monomeric aluminium concentrations from 3 to 197 μgl−1.2. Total invertebrate density (excluding Chironomidae) was correlated with pH (R2= 0.90, P&lt;0.05). Density of Ephemeroptera was more highly correlated with pH than density of invertebrates in other taxonomic orders. Invertebrate density (total and density of different orders) was generally more strongly correlated with pH than to inorganic monomeric aluminium concentrations.3. Species richness declined from sixty‐nine species at the highest pH site to thirty‐three species at the lowest pH site. Richness of Ephemeroptera and Trichoptera was positively correlated with pH (R2= 0.96 in both cases). Trichopteran richness was also negatively correlated with inorganic monomeric Al concentrations (R2= 0.96, P&lt; 0.05). Plecopteran richness was not related to stream acidity.4. Not all species of Ephemeroptera were negatively affected by low stream water pH. At low pH sites, Ameletus lineatus Traver (Family: Siphonoluridae) was relatively more abundant compared to other species of Ephemeroptera, and had greater biomass and greater weight per individual length than at higher pH sites.5. Differences in invertebrate community parameters among sites were not based on changes in food abundance. Although grazer densities were positively correlated with pH (R2= 0.93, P &lt; 0.05), differences in density were not related to differences in food. To the contrary, lower grazer densities occurred at the lowest pH site where measured food abundance (algae) was highest. Likewise, shredder density increased with increasing pH but was correlated with standing stocks of benthic organic matter (BOM), which had generally higher standing stocks at lower pH sites.6. Transplants of two species of Ephemeroptera between sites differing in pH (6.4 v 5.0) resulted in increased mortality of organisms placed at lower pH sites. In another transplant experiment, differences in mortality were not observed, although surviving invertebrates at low pH sites had ×10 higher body burdens of aluminium following the transplant than invertebrates from the reference site.7. These results indicate that direct effects of pH and Al (affecting survival) were more important than indirect effects of food availability in determining changes in invertebrate community structure between the study sites.

Fish species distribution in relation to water quality gradients in the North Branch of the Moose River Basin

The distribution of fish species in the North Branch of the Moose River (Lake Rondaxe to headwaters of Big Moose Lake) was determined by intensive netting and electrofishing surveys of lakes and streams in the watershed during 1982–83. A chronology of changes in fish species occurrence in the drainage system was reconstructed from earlier published surveys conducted in 1882 and 1931 and unpublished survey data obtained by the NYSDEC during the period 1948–1975. Native species present in 1882 were also collected in 1931. Smallmouth bass (Micropterus dolomieu) were introduced in the early 1900's and were present in collections made in 1931. Major changes in the fish community have taken place since 1931. The smallmouth bass and many of the native species found in the earlier surveys were either absent or restricted in occurrence to downstream sites (eg. L. Rondaxe and Moss L. sub-drainage) in 1982. Non-native species introduced after 1931 (yellow perch,Perca flavescens; central mudminnow,Umbra limi; banded killifish,Fundulus diaphanus) are currently widely distributed throughout the drainage system. In particular, the yellow perch is now a dominant species in the larger lakes of the basin. Comparisons of survival rates for caged fish transferred from high to low pH sites in the Big Moose drainage system demonstrated relatively greater acid tolerane of non-native species (yellow perch, mudminnow, killifish) than native cyprinids. Watershed acidity gradients (pH and aluminum concentrations) and relative physiological acid tolerance are major determinants of currently observed fish species distribution patterns in the North Branch of the Moose River. Differences in age and size structure of fish populations inhabiting acidic and non-acidic lakes of the drainage system were apparent, but difficult to interpret without additional information onpopulation size and potential density dependent parameters such as age specific growth and survival rates. Differential hatching success was observed for yellow perch eggs reciprocally transferred between acid (Big Moose) and neutral (Moss L.) lakes. Eggs transferred from Moss L. to Big Moose L. exhibited poor hatching success as a result of alterations in egg membrane structure that inhibited normal egg expansion and the hatching process. This effect was not evident in eggs from the same parents reared in Moss Lake nor in eggs from the Big Moose parents reared in both lakes. These experimental observations suggested possible genetic adaptation to acid stress by the yellow perch population inhabiting Big Moose Lake.

Bacterial Communities in Acidic and Circumneutral Streams

The relationship between pH and the abundance and activity of bacteria in streams was examined as part of a study of the effect of acidification on stream communities. Of the bacterial communities examined, the epilithic community appeared to be the most significantly affected by acidification. Microbial biomass, as quantified by measuring the ATP level, on rock surfaces was significantly correlated with pH. Also, bacterial production by the epilithic bacteria, indicated by incorporation of tritiated thymidine into DNA, was always higher at high-pH sites than at low-pH sites of the same stream order and elevation. Bacterioplankton concentrations varied between 0.53 x 10 and 9.42 x 10 cells . ml in the first- to fourth-order streams examined. The bacterioplankton concentration in one sample from a spring was 0.17 x 10 cells . ml. Bacterioplankton concentrations were not correlated with pH but were significantly correlated with seston concentrations. The correlation with seston is a result of increases in particle-associated bacteria at high seston concentrations. The proportion of bacterioplankton attached to particles varied from 0 to 70%. Bacterial numbers and production in the sediments were significantly correlated with the organic content of the sediment rather than with the pH of the overlying water. Thus, reduced abundance and activity of bacteria as a result of acidification could be detected only for the relatively active community on rock surfaces; this community was exposed to the low pH because of the unbuffered nature of its environment.